Zeolites and processes for their manufacture

Abstract

Colloidal Offretite, a process for its manufacture, and zeolite manufacture using it.

I claim: 
     
       1. A process for the manufacture of a colloidal suspension of Offretite, wherein a synthesis mixture having a molar composition, when calculated in terms of oxides, in the following ranges:   ______________________________________                                    
K.sub.2 O:Al.sub.2 O.sub.3                                                
               0.25 to 0.5:1                                              
  (TMA).sub.2 O:Al.sub.2 O.sub.3 at least 2.0:1                           
  SiO.sub.2 :Al.sub.2 O.sub.3  8 to 10:1                                  
  H.sub.2 O:Al.sub.2 O.sub.3  80 to 100:1                                 
______________________________________                                    
     wherein TMA represents the tetramethylammonium cation, is subjected to thermal treatment at a temperature and for a time sufficient to form a colloidal suspension of Offretite having a maximum dimension of at most 100 nm.   
     
     
       2. A process as claimed in claim 1, wherein the molar ratio of (TMA) 2  O:Al 2  O 3  is within the range of from 2.0 to 3.5:1. 
     
     
       3. A process as claimed in claim 1, wherein the thermal treatment is carried out at a temperature within the range of 40° C. to 100° C. 
     
     
       4. A process as claimed in claim 1, wherein the colloidal suspension is washed with water optionally cation exchanged, dried and optionally calcined. 
     
     
       5. The process of claim 1 wherein said K 2  O in said synthesis mixture is replaced with Na 2  O. 
     
     
       6. A process for the manufacture of Offretite which comprises forming an Offretite-forming synthesis mixture containing seed crystals of Offretite of maximum dimension at most 100 nm, and subjecting the seed-containing synthesis mixture to hydrothermal treatment at a temperature and for a time sufficient to form Offretite, said seed crystals prepared by the process of claim 1. 
     
     
       7. A process as claimed in claim 6, wherein the synthesis mixture has a molar composition, calculated in terms of oxides, in the following ranges:   ______________________________________                                    
M.sub.2 O:Al.sub.2 O.sub.3                                                
                1.3 to 4.0:1                                              
  (TMA).sub.2 O:Al.sub.2 O.sub.3 0.2 to 0.6:1                             
  SiO.sub.2 :Al.sub.2 O.sub.3  7 to 13:1                                  
  H.sub.2 O:Al.sub.2 O.sub.3  50 to 540:1                                 
______________________________________                                    
     wherein M represents an alkali metal cation, at least 70 molar per cent of which is represented by potassium, any remainder being represented by sodium.   
     
     
       8. A process as claimed in claim 6, wherein the synthesis mixture has a molar composition, calculated in terms of oxides, in the following ranges:   ______________________________________                                    
M.sub.2 O:Ga.sub.2 O.sub.3                                                
                1.3 to 4.0:1                                              
  (TMA).sub.2 O:Ga.sub.2 O.sub.3 0.2 to 0.6:1                             
  SiO.sub.2 :Ga.sub.2 O.sub.3  7 to 13:1                                  
  H.sub.2 O:Ga.sub.2 O.sub.3  50 to 540:1                                 
______________________________________                                    
     wherein M represents an alkali metal cation, at least 70 molar per cent of which is represented by potassium, any remainder being represented by sodium.   
     
     
       9. A process as claimed in claim 6, wherein hydrothermal treatment is carried out for from 2 to 10 hours. 
     
     
       10. The process of claim 3 wherein said seed crystals are present in said synthesis mixture at a level of from 0.0002 to 0.1% by weight of the total synthesis mixture. 
     
     
       11. The process of claim 10 wherein said seed crystals are present at a level of 0.01 to 0.05% by weight of said synthesis mixture. 
     
     
       12. A process for the manufacture of Offretite which comprises forming a synthesis mixture, substantially free from free organic structure directing agent, and having a molar composition, calculated in terms of oxides, in the following ranges:   ______________________________________                                    
M.sub.2 O:Al.sub.2 O.sub.3                                                
                     1.9 to 2.1:1                                         
  SiO.sub.2 :Al.sub.2 O.sub.3 9 to 11:1                                   
  H.sub.2 O:Al.sub.2 O.sub.3 140 to 180:1                                 
______________________________________                                    
     wherein M represents potassium, of which up to 30 molar percent may be replaced by sodium, and also containing seed crystals of Offretite of maximum dimension at most about 100 nm, and subjecting the seed-containing synthesis mixture to hydrothermal treatment for a time and at a temperature sufficient to form Offretite.   
     
     
       13. The process of claim 12 wherein said seed crystals are present in said synthesis mixture at a level from 0.0002 to 0.1% by weight of the total synthesis mixture. 
     
     
       14. The process of claim 13 wherein said seed crystals are present at a level of from 0.01 to 0.05% by weight of said synthesis mixture. 
     
     
       15. The process of claim 12 wherein said hydrothermal treatment is carried out at a temperature in the range of about 100° C. to 200° C.